BROOKLYN, Mich.—Brad Keselowski believes Penske Racing’s refusal to bend the rules contributed to him not being able to challenge Jimmie Johnson for the lead Sunday at Michigan.

Johnson was leading Keselowski with six laps remaining when his Hendrick Motorsports engine blew. Greg Biffle won the race and Keselowski finished second.

During the race, Keselowski made reference to Hendrick’s “tricks” with their cars. Hendrick’s Kasey Kahne and Dale Earnhardt Jr. finished third and fourth, respectively.

The Hendrick cars appear to have different rear suspension setups than other cars, especially at intermediate tracks such as Michigan, Indianapolis and Pocono.

“There’s part and pieces on the car that are moving after inspection that makes the cars more competitive,” Keselowski said after the race. “Some guys have it, some don’t. There’s a question as to the interpretation of the rule.

“Penske Racing errs on the safe side because we don’t want to be the guys that get the big penalty.”

Biffle said when NASCAR changed the rules raising the height of the bodies (the side skirts) earlier this year, teams had to adjust because the key is to get the car body to ride on the track as low as possible.

Roush Fenway has been making progress in that area, Roush said, and Biffle said it was the same technology that he has used in the past at some tracks, such as Kansas Speedway.

“We weren’t able to really perfect it,” Biffle said. “Then when the side skirts came about, we were committed—we had to go figure it out. Some guys just got it figured out faster than us.”

Keselowski said Penske will need to re-evaluate its setups.

“As a group at Penske Racing, we have not felt comfortable enough to risk that name and reputation that Roger has over those parts and pieces. Others have, which is their prerogative,” Keselowski said.

“I’m not going to slam it. But it’s living in a gray area. … We have to make a re-evaluation of that internally to decide if that’s the right way to go.”